Shooting 5k with Red Epic and cropping to 2:39:1 aspect ratio

Hello, I've seen a picture of Red Epic's frame guide that lists the 2:39:1 aspect ratio as an option. Does this mean that instead of using expensive anamorphic lenses to achieve 2:39:1 theatrical ratio, you can shoot 5k with round lenses, compose in camera for 2:39:1 and crop in post to the 2:39:1 ratio?
If so, it seems like this a step forward in technology.
Thanks - Craig

Only anamorphic glass will give you the characteristic anamorphic look and streak flares.

you could try to "fake it" by using the camera guides as a crop and then also using a streak filter on the lens. You'd be loosing some picture information. I think those guides are there to help when you are shooting with anamorphic glass.